Perylene diimide (PDI) based compounds represent an important class of opto-electronically active materials that have found utility in a wide variety of applications. [1] Such applications include active components in organic solar cells (OSC) [2-4], fluorescent probes used in imaging studies [5-7] chemical sensors [8-11] and semiconducting material in organic field effect transistors (OFETs) [12-14]. PDI based materials can be synthesized from relatively inexpensive starting materials, and have appreciable and tunable visible light absorption, strong self-assembly characteristics, and low-lying frontier molecular orbitals, that make them useful as electron transport materials in optoelectronic devices [3,15-19]
OSC's have the potential to provide low-cost, clean energy with minimal environmental impact. [20-22] Reliance on fullerenes as the electron transport material within the active layer of the highest performing devices. [23-27] Soluble POI based materials are being considered as attractive alternatives to fullerenes [17, 28-33]. Functionalized PDI materials exhibit a low lying lowest unoccupied molecular orbital (LUMO) which facilities electron transfer reactions, making them good electron acceptors. Importantly, functionalized PDI derivatives offer several advantages over fullerenes, including: low cost, synthetic modularity and increased light absorption in the visible region.
PDI molecules have been functionalized at the imide position with alkyl groups and at the bay position with aromatic units or certain heteroatoms to improve solubility and tailor self-assembly (Formula A) [3,19,34-37]:

For example, dimerization of the PDI chromophore and incorporation of the heteroatoms S or Se in the bay positions of the PDI framework. [3,36,37] provided a material having a remarkable effect on both its inter- and intramolecular properties, allowing the fabrication of OSCs with PCEs up to 7.1% and 8.4% for the S and Se annulated derivatives, respectively, when paired with tailor-made donor-acceptor type π-conjugated polymers [3,31,32]

Further derivatization of the dimers of Formula B is limited and large branched alkyl chains are required to ensure adequate organic solvent solubility.
A preferred PDI material to be used as an electron acceptor in OSCs will exhibit high solubility in organic solvents to allow for a diverse array of solution processing protocols to be employed, can be prepared by high yielding and scalable synthetic methods using atom-economical and sustainable chemistry practice, employ modular synthesis allowing for preparation of a library of diverse functionalized materials and maintain the key optical and electronic properties of related PDIs, including strong visible light absorption and deep LUMO energy levels. The present disclosure is directed to functionalized PDI materials useful, for example, as electronic acceptors in OSC's, to methods of making such materials as well as to devices made from such materials. More specifically the disclosure relates to nitrogen annulated PDI derivatives, methods of making them and to devices made from such materials.
A popular strategy for modification of the perylene chromophore is to install bromine atoms at the bay positions which can then be used as directing groups in a variety of carbon-carbon bond forming reactions to form 7-extended chromophores. PDI based materials derived from the bromination of the PDI chromophore are promising candidates for the replacement of fullerenes within a bulk heterojunction (BHJ) organic solar cell. A disadvantage of such materials is that they are made using an early bromination step that requires reaction over several days in dichloromethane with elemental bromine. This bromination produces isomeric forms of PDI and is therefore low yielding by nature. In addition, isolation of desired products in the presence of dibrominated isomers requires the use of column chromatography followed by several recrystallizations. The disclosure provides improved methods for the preparation of nitrogen annulated PDI materials.
Langhalls et al. [39] reported the synthesis of certain PDI materials having a heterocyclic pyrrolic unit installed at the bay position of the chromophore. While these materials were synthesized in good yields, they were not explored as electronically active materials to be self-assembled into superstructures useful for charge transport.